STAPHYLOCOCCUS AUREUS: IS RAW MEAT A RISK FACTOR FOR COLONIZATION AND INFECTION?

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: TERMINATED
• Funding Source: AFRI COMPETITIVE GRANT
• Reporting Frequency: Annual
• Accession No.: 0224993
• Grant No.: 2011-67005-30337
• Project No.: IOWW-2010-04418
• Proposal No.: 2010-04418
• Program Code: A4141
• Project Start Date: Apr 1, 2011
• Project End Date: Mar 31, 2016
• Grant Year: 2011

Project Director
Smith, T. C.

Recipient Organization
UNIVERSITY OF IOWA
Medical School
IOWA CITY,IA 52242

Performing Department
Epidemiology

Non Technical Summary
Several recent publications have documented a high prevalence of S. aureus in meat products. We seek to expand upon this research and examine the epidemiology of S. aureus associated with raw meat, and determine the effect of meat contamination with S. aureus on human colonization. We hypothesize that humans are exposed to S. aureus from food animals via handling of foods of animal origin.We will test this hypothesis by carrying out four objectives: 1) Determine the molecular epidemiology of S. aureus isolated from meat, humans, and the environment in two areas in Iowa. We will accomplish this using a prospective cohort study in Iowa. 2) Model the spread of S.aureus in this population, and determine the risk attributable to food in the acquisition of S. aureus 3) Determine the origin of food-borne S. aureus in order to examine the importance of contamination on-farm versus post-slaughter 4) Determine the effectiveness of an intervention derived from data collected in Aims 1-3. Our contribution will lead to an improved understanding of the epidemiology of S. aureus in the context of food-associated risk factors for human colonization. This contribution is significant as it will provide the knowledge needed to address the increasing public concern of MRSA acquisition from meat products; and to develop interventions on the farm or in the processing facility if food is found to be a risk factor for S. aureus acquisition, as hypothesized.

Animal Health Component

100%

Research Effort Categories

Basic

50%

Applied

50%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
712	3260	1170	12%
712	3320	1170	12%
712	3520	1170	12%
722	3320	1170	13%
722	3310	1170	13%
722	3510	1170	13%
712	3820	1170	12%
722	3299	1170	13%

Knowledge Area
722 - Zoonotic Diseases and Parasites Affecting Humans; 712 - Protect Food from Contamination by Pathogenic Microorganisms, Parasites, and Naturally Occurring Toxins;

Subject Of Investigation
3520 - Meat, swine; 3299 - Poultry, general/other; 3510 - Swine, live animal; 3820 - Goats, meat, and mohair; 3320 - Meat, beef cattle; 3260 - Poultry meat; 3310 - Beef cattle, live animal;

Field Of Science
1170 - Epidemiology;

Keywords

staphylococcus aureus

mrsa

raw meat

iowa

community sampling

zoonosis

zoonotic disease

antibiotic resistance

Goals / Objectives
Methicillin-resistant Staphylococcus aureus (MRSA) has been found in several recent studies investigating raw meat. Overall prevalence in meat samples has ranged from 2.5% to 11.9%. A recent study carried out in the United States found that 5% of meat samples tested in Louisiana were positive for MRSA, while 39.2% of samples were positive for any type of S. aureus. While S. aureus has previously been considered a food-borne pathogen, research examining S. aureus in food has largely focused on the toxins produced by food-borne S. aureus, and has not examined raw meats as a potential vector for colonization of consumers who handle raw meat products. Our central hypothesis is that S. aureus strains present on meat, including MRSA, may colonize individuals who handle raw meat. In order to investigate this hypothesis, we will carry out four specific objectives: 1) Determine the molecular epidemiology of S. aureus isolated from meat, humans, and the environment in two areas in Iowa. On the basis of our data presented under Preliminary Studies, our working hypothesis is that we will find a high diversity of strains, including isolates which are differentially distributed by source. 2) Model the spread of S.aureus in this population, and determine the risk attributable to food in the acquisition of S. aureus On the basis of our data presented under Preliminary Studies, our working hypothesis is that food has the potential to play a role in the transmission of virulent strains of S. aureus, similar to other environmental sources. 3) Determine the origin of food-borne S. aureus in order to examine the importance of contamination on-farm versus post-slaughter On the basis of our data presented under Preliminary Studies, our working hypothesis is that most meat isolates will originate from the farming environment, with typical "human" strains also playing a role in meat contamination. 4) Determine the effectiveness of an intervention derived from data collected in Aims 1-3. On the basis of the research carried out in Aims 1-3, we will develop, implement, and analyze an intervention designed to decrease the risk of acquisition of S. aureus from meat products. Expected outputs: peer-reviewed journal articles, eventual FAQ & advice sheets to consumers and potentially producers and/or processors.

Project Methods
In order to carry out these objectives, we will perform a prospective study, enrolling 100 families and collecting nose and throat samples from participants on a weekly basis. We will also collect environmental samples from the homes of these participants. These samples will be analyzed for the presence of S. aureus. Raw, retail-available meat samples will be purchased from local grocery stores where study participants shop and also analyzed for the presence and quantity of S. aureus present on meat products. High hand-touch areas in local grocery stores and homes will also be swabbed in order to isolate environmental S. aureus. The prevalence of S. aureus carriage in human participants and contamination of meat products and shared environments will be determined, and all isolates will be subjected to molecular typing. Using this information, we will examine the relative prevalence of S. aureus strains found in our meat and human samples, and employ geographic information system (GIS) modeling to examine their distribution within the community. We will also use risk factor questionnaire data from our participants in order to determine possible community and occupational exposures to S. aureus. We will use these data to determine the attributable risk for acquisition of S. aureus from raw meat products. Finally, we will compare molecular types isolated from meat to our database of S. aureus isolates from humans and animals in order to determine the amount of meat contamination that originates from the farm versus post-slaughter contamination, and design and implement an intervention to minimize transmission of this organism. At the conclusion of this study, we expect to have determined the impact of contaminated meat on human colonization with S. aureus, and determined the origin (human versus animal) of meat contamination. These results will have important implications for public health policy, including whether to begin routine, nationwide surveillance for MRSA on meat products.

Progress 04/01/11 to 03/31/16

Outputs
Target Audience: Consumers, Farmers, Policymakers, Researchers, public Health Workers. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? This project has provided continuous training opportunities for undergraduate and graduate students, and summer training opportunities for high school student volunteers. How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? The University of Iowa portion of this project (04/01 2011-08/15/2013) accomplished the specific aim 1 of this project: To determine the molecular epidemiology of S. aureus isolated from meat, humans, and the environment in two areas in Iowa. In order to achieve the specific objectives, two geographical areas, Iowa City and Keokuk County were selected for the longitudinal study. The IRB approval for this study was obtained from the Institutional Review Board of University of Iowa. Human subject enrollment began in 10/06/2011. Potential participants of both areas were contacted according to the study protocol, and human subject was recruited on the basis of inclusion criteria defined in the study protocol. All human participants gave written informed consent prior to enrollment. A total of 263 individual participants were enrolled as part of 95 family units. Human subject enrollment was completed in 01/04/2012, and 52 weeks of follow-up commenced for all participants. On a weekly basis, all human participants provided nasal and oropharyngeal swabs. Meat sampling started in 01/06/2012. Meat samples were purchased on a weekly basis from 8 grocery stores located in Iowa City and Keokuk County areas. These stores were chosen immediately following analysis of the enrollment questionnaire, in order to determine the most popular stores in both areas frequented by study participants and the most common brands of meat. Meat purchased include pork chop, ground pork, tenderized pork loin slice, bacon, ground beef, sirloin steak, New York steak, rib eye, ground turkey, chicken breast, chicken drumstick, and antibiotic free chicken breast. Environmental samples were also collected from high hand –touch areas within and surrounding of grocery stores using a pre – moistened, pre-enriched swab once in every month. These include cart handle, basket handle, movie kiosk, post office drop box, pop machine, ATM, and gas pump. All samples were processed immediately upon arrival, and were analyzed using established microbiology methods guided by the study protocol. All isolates positive for S. aureus were selected for molecular typing. Genomic DNA was extracted using the Wizard Genomic DNA preparation kit (Promega). The presence of PVL and mecA genes was determined by Polymerase Chain Reaction (PCR). Spa gene was sequenced. All molecular procedures employed known positive and negative controls. All human participants completed enrollment questionnaires. Questionnaires were focused upon capturing data on animal exposure in the previous year, demographic data, and behavioral data. One member of each house-hold also completed follow-up questionnaires weekly to identify types of meat products consumed and any other new exposures. Questionnaire and laboratory data were linked by a unique specimen number. All data from the prevalence survey and molecular tests are independently double-entered into databases and checked to ensure accuracy. The overall prevalence of S. aureus in meat and environmental samples is 27.8% (913/3290) and 13.4% (37/276) respectively. The overall prevalence of mecA and PVL gene among positive S. aureus isolates in meat samples is 2.8% (91/3290) and 2% (18/911) respectively. A total of 132 spa types were detected from 918 isolates from 913 contaminated meat samples. Overall, t002 was the most common spa type identified. Tetracycline resistance was observed for more than half of tested isolates belonging to CC398 (10/12; 83%), CC9 (15/23; 65%), and CC15 (13/23; 57%). A total of 3441 isolates were resulted from human samples. This project will be continued at Kent State University where research team will be focused on accomplishing the aim 2, 3 and 4 of this project.

Publications

Progress 04/01/12 to 03/31/13

Outputs
OUTPUTS: In order to achieve the specific aim 1 of this project, we continued 52 weeks of follow up for all participants. All human samples collection was completed by the end of January, 2012. We had twelve family units drop out of the study during its duration. This accounted for 21 adults and 13 minors. A total of 3274 isolates were obtained from human samples that include 93 methicillin resistant Staphylococcus aureus and 3181 methicillin susceptible staphylococcus aureus. We purchased 3290 pieces of meats from 8 different stores located in Iowa City and Keokuk County areas. Meat samples collection ended in December 31, 2012. All human, meat and environmental samples were cultured and confirmed as S. aureus according to the established microbiological methods defined in our study protocol using control samples for all tests. DNA extraction and glycerol stock are completed for all positive human meat and environmental isolates. Molecular typing is ongoing for human isolates. Selected isolated from all meat, human and environmental isolates are sent to the University of Iowa Hospitals and Clinics laboratory for antibiotic susceptibility testing by the broth dilution method. We determined the presence of PVL, mecA, and spa genes of all meat isolates via polymerase chain reaction. The Spa gene was sequenced. From the molecular analysis of S. aureus resulted from meat samples, we found diverse strain of MSSA and MRSA such as livestock associated, human and community associated strains. We did quantitation once in every month for all meat isolates to determine the level of S. aureus colonization that is measured in colony forming units per gram of meat. Participants completed questionnaires focused on capturing data on animal exposure in the previous year, demographic data, and behavioral data. Participants also completed follow up questionnaires weekly to identify types of meat products consumed and any other new exposures. Database for all human, meat and environmental samples was established and maintained. PARTICIPANTS: Tara C. Smith is the principle investigator for this project. Megan Quick was a project director from 06/2011 to 01/2012 and Co-project director from 01/2012 to 07/2012. Megan K Quick helped in questionnaire design, study design, participant enrollment, and bacterial culture. Dipendra Thapaliya is a Co-project director from 07/2012 to current date. Dipendra Thapaliya helped in meat sample collection, bacterial culture, and molecular analysis. Thomas M Meirick helped in data entry and bacterial culture. Ashley E Kates helped in study design, participant enrollment, bacterial culture, and molecular analysis. Sean OMalley helped in participant enrollment, bacterial culture, and molecular analysis. Ashley M Obrien helped in participant enrollment, bacterial culture, and molecular analysis. Sarah A Farina helped in participant enrollment, bacterial culture, and molecular analysis. James Y Wu helped in data entry, bacterial culture, and molecular analysis. Rushton G, Price L, and Meschke JS are collaborators for this project. This project has been providing continuous training opportunities for undergraduate and graduate students and summer training opportunities for high school student volunteers. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: We added quantitative methods to determine the level of S. aureus colonization in human samples.

Impacts
There is no significant outcomes or impact during this reporting period.

Publications

• Kates, A. E. (2012). Longitudinal study of Iowa families to characterize familial transmission dynamics and environmental exposures. Great Plains Emerging Infectious Diseases Conference, April, 2012
• Lin, V. (2012). Prevalence and molecular characteristics of Staphylococcus aureus in Johnson and Keokuk County in Iowa. SSTP Poster Session, July, 2012
• Meirick, T. (2013). Determining the prevalence of Staphylococcus aureus among two Iowa populations (abstract). ICRU Research in the Capitol, March, 2013
• Thapaliya, D. (2013). Commercially distributed meat as a potential vehicle for Staphylococcus aureus transmission (abstract). American Society for Microbiology, Denver, Colorado. May, 2013

Progress 04/01/11 to 03/31/12

Outputs
OUTPUTS: The specific aim 1 of this project is to determine the molecular epidemiology of Staphylococcus aureus isolated from meat, humans, and the environment in Keokuk County and Iowa City, Iowa. In order to achieve this aim, we designed longitudinal study. We obtained the IRB approval for this study from the Institutional Review Board of University of Iowa. Human subject enrollment began in 10/06/2011. Potential participants of both areas were contacted according to study protocol, and we recruited human subject on the basis of inclusion criteria defined in the study protocol. A total of 263 individual participants were enrolled as part of 95 family units. Human subject enrollment was completed in 01/04/2012, and 52 weeks of follow-up commenced for all participants. Meat sampling started in 01/06/2012. We purchased meat samples on a weekly basis from 8 grocery stores located in Iowa City and Keokuk County areas. These stores were chosen immediately following analysis of the enrollment questionnaire, in order to determine the most popular stores in both areas frequented by study participants and the most common brands of meat. Meat purchased include pork chop, ground pork, tenderized pork loin slice, bacon, ground beef, sirloin steak, New York steak, rib eye, ground turkey, chicken breast, chicken drumstick, antibiotic free chicken breast. Environmental samples were also collected from high hand touch areas within and surrounding of grocery stores using a pre moistened, pre-enriched swab once in every month. These include cart handle, basket handle, movie kiosk, post office drop box, pop machine, ATM, and gas pump. All samples were processed immediately upon arrival. Samples were analyzed using established microbiology methods guided by the study protocol. PARTICIPANTS: Tara C. Smith is the principle investigator for this project. Megan Quick was project director from 06/2011 to 01/2012. Megan K Quick helped in questionnaire design, study design, participant enrollment, and bacterial culture. Thomas M Meirick helped in data entry, and bacterial culture. Ashley E Kates helped in study design, participant enrollment, bacterial culture, and molecular analysis. Sean OMalley helped in participant enrollment, bacterial culture, and molecular analysis. Rushton G, Price L, and Meschke JS are collaborators for this project. This project has been providing continuous training opportunities for undergraduate and graduate students, and summer training opportunities for high school student volunteers. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
There is no significant outcomes or impacts during this reporting period.

Publications

• No publications reported this period